HANOI, Vietnam -- Vietnamese officials yesterday turned over previously unrevealed documents and films of captured and killed American servicemen to a congressional delegation seeking to determine the fate of 2,259 Americans who remain missing in action 20 years after the end of the U.S. war effort.

Americans and Vietnamese alike said the latest information could represent a significant advance in efforts to lay to rest, finally, a conflict that tore the fabric of American society. But the lingering bitterness of the struggle in Vietnam was evident on both sides during ceremonies at which the new materials were presented.

Vietnam's foreign minister complained that Americans show little sympathy for the 300,000 soldiers from his country whose fates are unknown and a U.S. senator upbraided the Vietnamese for trying to sugarcoat their record in dealing with prisoners of war.

"Today is Memorial Day in the United States, a day when we remember all our veterans of all wars," said Sen. John F. Kerry, D-Mass. "So it is a day of special focus on the issue" of what happened to those missing in action, or who were thought to be prisoners of war but did not return home when the Vietnam War ended.

"Those who have fought in wars -- and there are many here today -- know that you don't forget those you fought alongside of," said Mr. Kerry, who received three Purple Hearts, a Bronze Star and a Silver Star during service as a Navy gunboat officer in Vietnam. "The POW/MIA issue is a difficult one for both sides."

Elderly Vietnamese military leaders, some of them moist-eyed, nodded gravely at his words, but the mutual empathy was fragile.

Speaking before Mr. Kerry, Nguyen Manah Cam, Vietnam's foreign minister, told U.S. congressmen and representatives of veterans associations attending the opening of a U.S.-Vietnamese archive for information on U.S. servicemen missing in action that "it was not ourselves who created the war."

"Our people are now questioning our Congress members," Mr. Cam declared. "They are saying that our people have made a lot of efforts to help the American side resolve their MIA cases, but what has the American side done to help us resolve our MIAs?

"We would like the U.S. side to provide the name, age and hometown of Vietnamese servicemen who were captured, died and were buried somewhere," he said, reflecting the sort of information the United States is demanding from the Vietnamese.

Mr. Kerry and the delegation he heads -- which includes Sen. John H. Glenn, D-Ohio, and Rep. Pete Peterson, D-Fla., who was a POW for more than six years in Vietnam -- asked the Vietnamese to allow inspection of government records at a level, according to one American official, the United States would not consider opening.

Air Force Maj. Robert L. Overturfs, spokesman for the U.S. military task force attempting to make a full accounting of American POWs and MIAs, said that while "the Vietnamese have made clear to us that there [are] still outstanding national security concerns" in those records, "we are talking about the fact that these are documents 20 years old and older, that couldn't have more than an oblique bearing" on national security.

However, officials in the United States -- in Washington and at the John F. Kennedy Presidential Library in Boston -- recently declined to open records of the Vietnam War era, also citing "national security" concerns.

The congressional delegation and its support staff of forensic and intelligence experts from the armed services were enthusiastic about the new materials handed over by the Vietnamese yesterday, which included a full register of prisoners taken by the Vietnamese side beginning in 1964, and 229 reels of film, some of which are believed to have been shot where downed U.S. aircraft crashed.

"There should be some information about the unaccounted-for [servicemen]," said Robert DeStatte of the Defense Intelligence Agency. "I don't think we'll necessarily find a whole lot, but there is potential."

Mr. Kerry said Foreign Minister Cam's sharp remarks constituted "a very direct message that they're giving us an enormous amount of effort and despite their knocking themselves out there continues to be questions about their effort and their honesty."

Noting that the Vietnamese already have produced 3,000 documents in attempts to satisfy American questions, Mr. Kerry said, "I understand their frustration. We are pushing hard. That's our job. I do think that we're getting there."